Decreasing Oscillations Of Aerial Cranes

Aerial cranes refer to the transportation of heavy payloads suspended fromcables on helicopters. The aerial crane is one of the main uses of helicopter in bothmilitary and civilization domain. Compared with non-slung-load flight, gravity loadshould be considered in the slung-load system. When a heavy load is carried, the loadoscillates in response to helicopter motion and disturbance forces, such as wind. Thisoscillation is dangerous and adversely affects control of the helicopter, especiallywhen carrying large or heavy loads. Therefore, the study of swing control systems isessential for safe and efficient transportation.The modeling and dynamics of the planar and three-dimensional aerial cranes arederived. This thesis proposes the oscillation mechanism of the aerial crane system.The varying suspension cable lengths and mass ratio have great effect on the transientdeflection and residual amplitude of the payload swing and helicopter speed underthree kinds of motion system. Simulations and experiments were used to verify thekey dynamic behavior. So this thesis provides fundamental basis for decreasingoscillations of aerial cranes.This thesis proposes a novel command smoothing technology, which cansuppress the oscillations of both the payload and helicopter effectively. Thistechnology is a feedforward control method, which is designed based on thefrequencies and damp ratio of the system. The command smoothed by the commandsmoother will suppress the vibration below a low level. Zero vibration will beachieved when the model is correct and the robustness of the smoother is excellent.The technology is used to control the vibrations of aerial cranes systems. What’smore, excellent vibration suppression is achieved for the nonlinear systems.Many scientists have worked to provide solutions to the challenging problemsposed by the payload swing for the aerial cranes. While significant work has beendirected at eliminating the payload swing, less effort has been placed on designing acontrol scheme for suppressing oscillations of the helicopter speed. In this thesis, wealso study the oscillations of the helicopter speed. Furthermore, control of not only theresidual but also the transient vibrations is reported. Simulations and experimentalresults obtained from a model aerial crane validate the effectiveness of the method. Both the payload swing and oscillations of helicopter speed are suppressed greatly.